Aquaponic Gardening

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Hi!

Introducing my first aquaponic system which is under construction.

It will be a flood-and-drain system, with the grow bed raised to waist level, and draining back into the fish tank. I haven't planned a sump or reserve reservoir, just keep it simple: one fish tank, one grow bed. The volume of water in the fish tank is almost the same as the volume of gravel in the grow bed.

Here are some pictures. Let's start with the fish: 10 Mozambique tilapia, currently indoors, fertilizing my pot plants.

Next, here's my greenhouse, which I will need to move, because it's placed too shady by the previous owners of this house. I hope to move it in April, if I get a whole bunch of friends to come here and help me carry it! It's only 10 square metres (107 square feet).

Next is my fish tank, which is 300 litres (79 gallons), standing on edge in a shed. I got it for free, because it has a leak. Due to a misconstruction in the first place, it will always leak, whatever you try, but the leak is so small that I'll lose no more water than through evaporation. It's just not a tank for indoors.

Here's my grow bed that I'm currently building. I'm re-using some recycled-plastic boards as the sides. The bottom is a really hard and heavy board that I found in a waste container. I will line this with some pond liner, and plan to make a home made bell siphon to empty it.

Finally, this is crushed lava gravel that I have left over from a roof garden that I rebuilt. I'll have to wait for the snow to melt before I can check if I have enough of it, or if I'll have to make a mixture of this and Leca (=Hydroton), or ordinary gravel.

I plan to grow cucumbers, tomatoes, basil, lettuce, and maybe wild strawberries in it this first year.

If my plan holds up, I'll have this system up and running in May this year! However, work will pile up on me as soon as spring comes, so I try to prepare all I can while it's still winter. There's always a risk that I won't make it this year, but let's hope!

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Add a T just above the pump and add a valve so you can open up flow back into the sump tank so that the pump doesn't overflow the fish tank.

But you may simply want to get a different pump to save you some money on electricity if you don't need such a big pump.

However, for an IBC fish tank I would probably be going with a 3" drain.  32mm drains, even if you have two of them, are just too small.  2" or 50mm is probably the smallest size drain I would use on a fish tank big enough to grow edible fish.

unless I'm mistaken, you've got a 400W pump that moves 150 liters per minute. I think that's about 2500 gallons per hour. That might be a bit overkill for a system of your size.

Beth - Yes, I'm considering it now. I chose to not use the lava rock, as I used it in my indoor system, and don't like how hard it is on fingers and roots. But as a bottom layer would be ok. Until I clean it out, and it all gets mixed up, somewhere along the road.

TCLynx - I haven't been able to find a bulkhead fitting larger than these anywhere. But I'll hunt around for something bigger.

Jeffrey - Yes, I'll be looking for another pump, and I see how I can easily go for a smaller one. I was following the advice in Sylvia Bernsteins book to oversize a bit...:P

But the main problem is still there - the float was so unreliable and impossible to finely adjust. That problem remains to solve - how do I ensure that the pump never runs dry?

If it is a one pump system, I don't think a float switch is appropriate.  Now if the pump and sump tank size are totally mismatched and inappropriate to the system I fear it may never work very well for you even if the float switch was easy to adjust.  Float switches are notoriously difficult and failure prone.

You may find you have to go to the internet for find some types of plumbing fittings.  I don't know what the true pipe sizes there are so I'm not going to suggest uniseals to you since I've heard that The PVC pipe sizes and fittings in Europe don't match up with the pipe sizes here in the USA..

Even if you get a somewhat smaller pump you can still oversize a bit.  I think the pump you have is probably a bit more than twice the size you need.  A 4000 liter per hour pump would be appropriate and over sized enough unless you are planning on adding several more greenhouses to the same system in the next several months.

You should still add the bypass since you will have to adjust the amount of flow.

Here is a diagram for a simple system that shows the bypass as well as many other helpful tips.

In my original plan, I was going to have the fish tank below the grow beds, and no sump. But then I bought an IBC tank for the fish, partly because my aquarium wasn't great, and partly to give me more water volume, for when I want to add another grow bed. So now, with the IBC being rather high, I put the grow beds lower. Meaning that I can't do without the sump tank. However, I can plumb two sumps together (another blue barrel) to increase my sump volume.

If float switches are not reliable, then how do you make sure the pump never runs dry? If it's sitting in the fish tank, of course there's no problem, but then I have to dig a great big hole in the ground to lower the IBC a great deal. Other people do have pumps in the sump, how do they do it? Oversize the sump, and have a weak pump set on timer?

Since the system I have built is a CHIFT PIST, I can't see how I can use the tips in this diagram.

TCLynx said:

If it is a one pump system, I don't think a float switch is appropriate.  Now if the pump and sump tank size are totally mismatched and inappropriate to the system I fear it may never work very well for you even if the float switch was easy to adjust.  Float switches are notoriously difficult and failure prone.

You may find you have to go to the internet for find some types of plumbing fittings.  I don't know what the true pipe sizes there are so I'm not going to suggest uniseals to you since I've heard that The PVC pipe sizes and fittings in Europe don't match up with the pipe sizes here in the USA..

Even if you get a somewhat smaller pump you can still oversize a bit.  I think the pump you have is probably a bit more than twice the size you need.  A 4000 liter per hour pump would be appropriate and over sized enough unless you are planning on adding several more greenhouses to the same system in the next several months.

You should still add the bypass since you will have to adjust the amount of flow.

Here is a diagram for a simple system that shows the bypass as well as many other helpful tips.

Essentially you need a big enough sump tank to handle flooding your grow bed while sill having enough water in it to keep your pump from running dry.

The diagram shows useful things like having a bypass on the pump so excess flow can be sprayed back into the tank the pump is in if your pump is too fast for your plumbing.

If you want to look up other diagrams my web site has lots of them in my plumbing class presentations.

TCLynx Aquapnic Plumbing class 2011

There are examples of CHIFT PIST or CHOP systems in there.

Since your pump is so strong, it might actually make more sense for you to set up your system as a CHOP mark 2 where your pump feeds the fish tank and grow beds separately and the fish tank and grow beds all drain back to the sump directly.  This should help use more flow from your pump while reducing the overflow problem with your fish tank not having large enough drains to handle the flow.  (However, 32 mm drains still seem too small to me to handle the flow needed for an IBC size fish tank unless you are only going to stock a hand full of small fish.

Yep, you basically just need a big sump tank, and a pump that has an very low intake is good too.

I will get another pump.

I was wondering about sump tank size in another thread there before I built it. My question was how to calculate the amount of water I could expect once my 300 litre grow bed is full of media. I got the answer 40-50%. In that case my 200 liter sump would have been ok. 

The question now is if it still is ok when I change to a slower pump, or if I still need to increase the sump too. Do you know if it works to plumb two barrels together from the lower parts? So far, the 32 mm bulkheads are the biggest i have found, so that's the size the connection can be.

Thanks for supporting me in this!

You probably could plumb two barrels together.

Remember that you will loose a little of that 200 liter volume to having cut the side out of the barrel.

Have you looked to see if you can get fittings that thread into the bung hole threads on the barrels?  Usually the barrels have one bung that has fine threads that match up with plumbing fittings and then the other bung is coarse threads and harder to find fittings to match.

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